<!doctype html>
<style>
  body {
    margin: 0;
    padding: 0;
  }

  div {
    position: absolute;
    top: 0;
    left: 0;
    width: 500px;
    height: 500px;
    background: green;
  }
</style>
<div></div>
<script>
  var clicks = []
  document.querySelector('div').addEventListener('click', (e) => clicks.push([e.clientX, e.clientY]))
</script>
